river outlet core [15] presents the following pattern (Fig. 12): (1) an emergence of
contamination in 1950, as in the Rhône River [17], (2) a sharp increase until 1960,
(3) then a 15-year plateau between 1,500 and 2,200 μg kg
À1 until 1975 followed by
(4) an exponential decrease to 200 μg kg
À1 in 2005. The Lower Seine River was
under critical contamination from 1955 to 1980 when applying the criteria for
dredged sediments in rivers (Nr ¼ 680 μg kg
À1 ) and from 1952 to 2005, when
using those for estuaries (Ne 2 ¼ 160 μg kg
À1 ) [84]. When the PCB content exceeds
these levels, the sediment should be treated or appropriately stored [83]. This trend is
confirmed by that observed in the estuarine Rouen core [26], which covers the period
from 1968 to 2008: the maximum contamination is noted in 1972, as in the
OUT 1 core, with total PCBs at 4150 μg kg
À1 , and then a regular 30-fold decrease
to 140 μg kg
À1 . The higher contents in the estuary can be attributed to direct sources
and to finer sediments in this core (Al contents at 4% vs 3% in the Seine River SPM).
Highly polluted estuarine sediments and agricultural soils in the Seine River floodplain are a long-term contamination heritage. When the second crisis was triggered
in 2005, the PCB contamination was already reduced by a factor of 20–30 compared
to the 1970s: at that time it was probably considerably above the current WHO
criteria that could have resulted in health problems for regular fish and seafood
consumers, but this issue was not detected. Sedimentary records unveil this past
environmental history.
9 Conclusions
The emergence of new water quality issues is continuous as scientific knowledge
progresses and analytical capacities are developed to detect new deleterious substances at reduced costs. Environmental regulations are evolving as well, but with a
time-lapse of several years or decades between the start of use of a compound and its
recognition as a potentially harmful agent to the environment or health. For the
micropollutants studied in the PIREN-Seine programme, the medium time lapse is at
least 30 years. Furthermore, the environmental release of many of these xenobiotics
is not regulated, such as for antibiotics. It is common knowledge that resources are
lacking to implement surveys dedicated to unregulated compounds. Finally, as in the
case of PCBs, the regulatory survey which followed the water compartment was not
adequate, missing the target media: biota and SPM. If the biota is now included as a
target media in the WFD, SPM guidelines are still lacking.
Sedimentary archives make it possible to document the long-term state of
the river quality for many issues. Water quality trajectories should then be
complemented by substantial research on environmental history: (1) definition and
recognition of the issue, with effects, causes, control factors, indicators, metrics,
criteria and/or scales of water quality; (2) implementation of sustainable observatories for long-term monitoring and surveillance on proper media, at proper stations
and frequencies, with appropriate analytical tools; (3) assessment of water quality
and its declaration by relevant authorities; (4) identification of the origin(s) of the
Sedimentary Archives Reveal the Concealed History of Micropollutant. . .
295
contamination in 1950, as in the Rhône River [17], (2) a sharp increase until 1960,
(3) then a 15-year plateau between 1,500 and 2,200 μg kg
À1 until 1975 followed by
(4) an exponential decrease to 200 μg kg
À1 in 2005. The Lower Seine River was
under critical contamination from 1955 to 1980 when applying the criteria for
dredged sediments in rivers (Nr ¼ 680 μg kg
À1 ) and from 1952 to 2005, when
using those for estuaries (Ne 2 ¼ 160 μg kg
À1 ) [84]. When the PCB content exceeds
these levels, the sediment should be treated or appropriately stored [83]. This trend is
confirmed by that observed in the estuarine Rouen core [26], which covers the period
from 1968 to 2008: the maximum contamination is noted in 1972, as in the
OUT 1 core, with total PCBs at 4150 μg kg
À1 , and then a regular 30-fold decrease
to 140 μg kg
À1 . The higher contents in the estuary can be attributed to direct sources
and to finer sediments in this core (Al contents at 4% vs 3% in the Seine River SPM).
Highly polluted estuarine sediments and agricultural soils in the Seine River floodplain are a long-term contamination heritage. When the second crisis was triggered
in 2005, the PCB contamination was already reduced by a factor of 20–30 compared
to the 1970s: at that time it was probably considerably above the current WHO
criteria that could have resulted in health problems for regular fish and seafood
consumers, but this issue was not detected. Sedimentary records unveil this past
environmental history.
9 Conclusions
The emergence of new water quality issues is continuous as scientific knowledge
progresses and analytical capacities are developed to detect new deleterious substances at reduced costs. Environmental regulations are evolving as well, but with a
time-lapse of several years or decades between the start of use of a compound and its
recognition as a potentially harmful agent to the environment or health. For the
micropollutants studied in the PIREN-Seine programme, the medium time lapse is at
least 30 years. Furthermore, the environmental release of many of these xenobiotics
is not regulated, such as for antibiotics. It is common knowledge that resources are
lacking to implement surveys dedicated to unregulated compounds. Finally, as in the
case of PCBs, the regulatory survey which followed the water compartment was not
adequate, missing the target media: biota and SPM. If the biota is now included as a
target media in the WFD, SPM guidelines are still lacking.
Sedimentary archives make it possible to document the long-term state of
the river quality for many issues. Water quality trajectories should then be
complemented by substantial research on environmental history: (1) definition and
recognition of the issue, with effects, causes, control factors, indicators, metrics,
criteria and/or scales of water quality; (2) implementation of sustainable observatories for long-term monitoring and surveillance on proper media, at proper stations
and frequencies, with appropriate analytical tools; (3) assessment of water quality
and its declaration by relevant authorities; (4) identification of the origin(s) of the
Sedimentary Archives Reveal the Concealed History of Micropollutant. . .
295